Consider using the Playwright container image for e2e tests in CI

[praseodym]

Installing Playwright browsers using pnpm playwright install --with-deps --no-shell in GitHub Actions takes at least a minute and sometimes up to 15 minutes when the apt mirror is slow.

We should consider using the Playwright container image for e2e tests:

• [Feature] Faster way to install Playwright Browsers and dependencies on GitHub Actions microsoft/playwright#23388 (comment)
• https://playwright.dev/docs/ci#via-containers

[praseodym]

We just had a run where installing Playwright browsers took 26m 7s: https://github.com/kiesraad/abacus/actions/runs/22357594419/job/64701862586

Fetched 198 MB in 25min 17s (131 kB/s)

😪

[praseodym]

I stopped this job after more than an hour of installing just dependencies for Chromium: https://github.com/kiesraad/abacus/actions/runs/22435797073/job/64965166694